Paper making



United States 2,999,789 PAPER MAKING Paul Quinn, Bath, England, assignor to W. S. Hodgkinson &"Company Limited, Wells, England No Drawing. Filed Mar. 31, 1958, Ser. No. 724,863 Claims priority, application Great Britain Apr. 2, 1957 4 Claims. (Cl. 162201) .aftent The synthetic resins preferred for use in this invention are polymerisation or condensation products formed with melamine monomer. This is substantially water insoluble and may conveniently be incorporated in pow- .der form into the fibre pulp from which the paper web is manufactured, and thereafter reacted in situ with any other suitable resin-forming component, such as preferably formaldehyde or hexamethylene tetramine.

In a preferred process, all the necessary resin-forming components, usually two in number, are incorporated in the paper web during manufacture. These components must of course be each substantially water-insoluble and in unreacted form. 'Where formaldehyde is one of the components, it is therefore conveniently incorporated in the form of paraformaldehyde.

Alternatively, a substantially water-insoluble semicuredresin such as a B-stage melamine-formaldehyde syrup. After drying, the impregnated paper is cut to size and pressed on to background material. I

These known methods have a number of disadvantages; First, "the paper must be highly absorbent since it is impregnated with the syrup after it has been made, so that printing is difficult, and all the more so because the paper must be printed from the reel to enable it to be easily dipped in the resin solution. Second, after the impregnated paper has been dried. it is hard and brittle, so that it is liable to be damaged by breakage, especially if handled mechanically. Third, off-cuts removed after drying of the impregnated paper cannot be re-used. Fourth, the impregnated paper is extremely sensitive to moisture, heat and ageing. According to the present invention there is provided a process of making paper filled with a synthetic resin, in which a substantially water-insoluble resin-forming component is incorporated in the paper web before completion of the manufacture thereof, and thereafter reacted with another resin forming component to form the synthetic resin in situ within the web.

Since the paper is thus not required to be impregnated by a resin syrup, it may and should be formed; with a smooth, close surface which facilitates printing.

A simplified flow diagram of the process is as follows:

I B v ian I insoluble melamine monomer -----i paraformaldehyde i Paper web formed on paper-making machine Printed paper web formaldehyde Uncured resinfilled paper Laminate formed by hot pressing condensation product, can be incorporated in the pulp from which the paper Web is formed.

The invention specifically includes as a new article of manufacture, paper incorporating at least one unreacted resin-forming component within the web. The invention will be more readily understood from the following description of three alternative examples of processes for making resin-impregnated paper, given however by way of illustration only.

Example I In the first process, melamine or like monomer in powder form is incorporated with the pulp before the Web is formed on the paper-making machine.

The paper-making process is controlled tov give a smooth, close surface finish to the formed web, which is Well able to receive subsequent printing. If desired, the

surface can be made suitable for printing from half-tone blocks. The paper web may if desired be cut up into sheets before printing, or can be printed from the reel. Off-cuts can be returned to the pulper.

After printing, the other resin-forming component, e.g. formaldehyde, is applied to the paper inany convenient manner, either as a solution or invapo'ur form- Solu tions are applied preferably in the form of a spray.

and formaldehyde react together.

The paper is subsequently dried with heat in a ventilated dryer, and when dry, the paper is hot-pressed on to the background, during which operation the melamine Example II In an alternative and preferred method, both resinforming components are incorporated in the paper web. Thus both melamine monomer and formaldehyde, in the form of substantially water-insoluble paraformaldehyde, are incorporated as powder in the pulp from which the paper web is made. Printing of the web is then effected as described above, and the melamine and formaldehyde are reacted together to form the desired synthetic resin when the printed paper is hot-pressed on to the background.

The process just described has the outstanding advan- Air dry rag pulp 114 Melamine monomer 168 Patented Sept. 12, 1961 The amount of melamine monomer may be varied to give between 25 and 50% of melamine in the finished paper and, if desired, suitable heat resisting dyes and.

coloured pigment may also be included to give paper of any desired shade.

Example III In another preferred method of resin-forming components are introduced into the pulp as a substantially water-insoluble semi-cured material. The paper is then made, printed and hot-pressed as before. As in the case of Example II, the paper requires no treatment'after printing except hot-pressing on to the background.

The material should not be more than 0.75% water soluble, or too much will be lost during manufacture of the web. The preferred material is again a water-insoluble, B-stage melamine condensation resin, such as rnel amine formaldehyde. 7

In all of these processes the paper produced can be printed better than was possible in the production'of previously known resin-impregnated papers. It is moreover soft and pliable, dimensionally stable, unaffected by moisture, and has an excellent storage life.

It will be appreciated inthe examples given above, using melamine as one of the resin forming components, the other component can be any other suitable compound besides formaldehyde, such for example as hexamethylene tetramine.

I claim:

1. A process for the production of synthetic resin-filled paper suitable for the productionof decorative and Wearresistant laminates which comprises the steps of incorporating substantially water-insoluble melamine monomer in a fibre pulp, manufacturing a paper web with a smooth close surface which facilitates printing from said fibre pulp, printing the paper web, and treating the printed paper web with formaldehyde in the molar ratio of from 1 to 3 moles of formaldehyde per mole of melamine to convert the melamine to partially condensed melamineformaldehyde resin in situ within the paper web, the amount of melamine employed being such as to constitute from 25 to 50% of the weight of the resin-filled paper.

2. A process for the production of synthetic resinfilled paper suitable for the production of decorative and wear-resistant laminates which comprises the steps of incorporating substantially water-insoluble melamine monomer and substantially water-insoluble paraformaldehyde in the molar ratio of from 1 to 3 moles of paraformaldehyde per mole of melamine in a fibre pulp, manufacturing a paper web with a smooth close surface which facilitates printing from said fibre. pulp, partially condensed melamine-formaldehyde resin being formed in situ within the paper web from said melamine and paraformaldehyde, and printing the paper web, the amount of melamine employed being such as to constitute from 25% to 50% of the weight of the resin-filled paper.

3. A process for the production of decorative and wear-resistant laminates which comprises the steps of incorporating substantially water-insoluble melamine monomer in a fibre pulp, manufacturing a paper web with a smooth close surface which facilitates printing from said fibre pulp, printing the paper web, treating the printed paper web with formaldehyde in the molar ratio of from 1 to 3 moles of formaldehyde per mole of melamine to convert the melamine to partially condensed melamine formaldehyde resin in situ within'thc paper web, the amount of melamine employed being such as to constitute from 25% to 50% of the weight of the resin-filled paper, and hot-pressing the resin-filled paper on to a least one sheet of background material.

4. A process, for the production of decorative and wear-resistant laminates which comprises the steps of incorporating substantially water-insoluble melamine monomer and substantially water-insoluble paraforrnaldehyde in the molar ratio of from 1 to 3 moles of paraforrnaldehyde per mole of melamine in a fibre pulp, manufacturing a paper web with a smooth close surface which facilitates printing from said fibre pulp, partially condensed melamine-formaldehyde resin being formed in situ within the paper web from said melamine and paraformaldehyde, printing the paper web, the amount of melamine employed being such as. to constitute from 25% to 5 0% of the weight of the resin-filled paper, and hotpressing the resin-filled paper on to at least one sheet of background material.

References Cited in the file of this patent V UNITED STATES PATENTS 

1. A PROCESS FOR THE PRODUCTION OF SYNTHERIC RESIN-FILLED PAPER SUITABLE FOR THE PRODUCTION OF DECORATIVE AND WEARRESISTANT LAMINATES WHICH COMPRISES THE STEPS OF INCORPORATING SUBSTANTIALLY WATER-INSOLUBLE MELAMINE MONOMER IN A FIBRE PULP, MANUFACTURING A PAPER WEB WITH A SMOOTH CLOSE SURFACE WHICH FACILITATES PRINTING FROM SAID FIBRE PULP, PRINTING THE PAPER WEB, AND TREATING THE PRINTED PAPER WEB WITH FORMALDEHYDE IN THE MOLAR RATIO OF FROM 1 TO 3 MOLES OF FORMALDEHYDE PER MOLE OF MELAMINE TO CONVERT THE MELAMINE TO PARTIALLY CONDENSED MELAMINE TO FORMALDEHYDE RESIN IN SITU WITHIN THE PAPER WEB, THE AMOUNT OF MELAMINE EMPLOYED BEING SUCH AS TO CONSTITUTE FROM 25% TO 50% OF THE WEIGHT OF THE RESIN-FILLED PAPER. 